1. Field of the Invention
The invention relates to a frequency control system and method, and particularly, to a lamp frequency control system for a display and method for controlling lamp frequency.
2. Description of the Related Art
Referring to FIG. 1, for a conventional lamp 11 of a display (such as a liquid crystal display), a direct current (DC) is converted to an alternating current (AC) by a converter 12 to supply a desired power to the lamp. A display panel 15 of the display is driven by a driving device 16 to display. The driving modes of the conventional driving device 16 include various modes, such as dot inversion and column inversion modes. Each of the driving modes has a different driving manner and scanning frequency.
As currently known, a water flow interference may be induced by the interaction of the operating frequency and the scanning frequency of the converter. There are three conventional solutions for improving the water flow interference, wherein the first solution is to shield the electromagnetic interference with a indium tin oxide (ITO) layer; the second solution is to employ a converter having an operating frequency in sync with a horizontal scanning frequency; and the third solution is to alleviate the water flow interference by offsetting the intensity of the electric field interference with two neighboring lamps of opposite polarities.
However, the first solution has a high cost, and the ITO layer will be etiolated due to the quality problem, thereby inducing color difference. In the second solution, the horizontal scanning frequency must be precisely locked where any variation may immediately lead to the water flow interference. The third solution is only to alleviate the water flow interference, but no capable of completely eliminating the water flow interference.
In addition, the conventional driving device 16 may be controlled by switching between at least two driving modes (such as dot inversion and column inversion). However, under the driving mode switching condition, it is impossible to lock the horizontal scanning frequency precisely to match the operating frequency of the converter. Therefore, for a display having a driving device with at least two driving modes, the second solution cannot be employed to resolve the water flow interference.
Therefore, it is necessary to provide a lamp frequency control system for a display and method for controlling lamp frequency to resolve the abovementioned problem.